Swirls of plankton decorate the Arabian Sea

Winter blooms of Noctiluca scintillans may be disrupting the marine ecosystem

satellite image of plankton in Arabian Sea

SCINTILLATING SWIRLS  In a satellite image taken February 3, plankton blooms appear as green whorls in the Arabian Sea. In recent years, an algae-filled plankton species has been changing the ecology of these waters. 

MODIS-Aqua Ocean Color Data/NASA

Masses of plankton add swirls of green to the blue waters of the Arabian Sea in this February 3 snapshot from NASA’s Aqua satellite (Iran and Pakistan at top of the image; India, to the right). Most of the vibrant color probably comes from algae living in the single-celled bodies of the dinoflagellate Noctiluca scintillans.

N. scintillans started appearing in the Arabian Sea in large numbers in the early 2000s, blooming in the winter months. It seems that the plankton, which love low-oxygen waters, have made a happy home in the increasingly oxygen-poor Arabian Sea, says marine ecologist Joaquim Goes of Columbia University.

Some N. scintillans house green algae (dark patches) in their bodies, which measure 0.2 to 2 millimeters across. J. Goes/LDEO/Columbia Univ.
That’s bad news for local ecosystems. N. scintillans feasts on the sugar its internal algae make from sunlight, but the dinoflagellate also eats anything smaller than itself, Goes says. “It becomes very difficult for other organisms to survive.” Few species chow down on N. scintillans, and evidence suggests that the plankton is “short-circuiting” marine food webs, Goes says.

N. scintillans and its algae may also be warming their surroundings by changing how incoming sunlight is absorbed at the sea’s surface. Such warming waters could be contributing to the recent uptick in Arabian Sea cyclones, Goes says. “What we see now is a complete change of that ocean.”

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